(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of forming high quality nickel silicide in the fabrication of integrated circuits.
(2) Description of the Prior Art
The major factors that effect the formation of nickel silicide include the presence of native oxide, the cleanliness of the silicon surface, and the presence of oxygen during rapid thermal annealing (RTA). In manufacturing, the major hindrance to forming a high quality nickel silicide is the presence of native oxide. For example, device wafers on queue for nickel deposition may encounter delays from the unexpected malfunction of the nickel deposition equipment. These delays allow for the growth of native oxide on the silicon surface. Unlike titanium, nickel is unable to reduce oxide on the substrate surface. Therefore, the native oxide will act as a diffusion barrier, preventing the diffusion of nickel into the silicon to form nickel silicide. It is desired to find a method to remove the native oxide before nickel silicidation.
A number of patents teach nickel silicidation. U.S. Pat. No. 6,037,254 to Hong discloses a protective oxide layer to prevent alteration of contaminants on a silicon surface before deposition of a nickel layer. U.S. Pat. No. 6,066,547 to Maekawa, U.S. Pat. No. 5,075,259 to Moran, and U.S. Pat. No. 5,773,329 to Kuo teach various silicide processes.
A principal object of the present invention is to provide an effective and very manufacturable method of fabricating a nickel silicide film in the fabrication of an integrated circuit.
A further object of the invention is to provide a method of avoiding native oxide contamination while fabricating a nickel silicide film in the fabrication of an integrated circuit.
Yet another object is to provide a method of removing native oxide in the process of forming a nickel silicide film.
Yet another object is to provide a method of removing native oxide with a titanium capping layer in the process of forming a nickel silicide film.
A further object is to provide a method of removing native oxide with a titanium/titanium nitride capping layer in the process of forming a nickel silicide film.
A still further object of the invention is to provide a method of removing native oxide with an atomic layer of titanium underlying nickel in the process of forming a nickel silicide film.
Another still further object of the invention is to provide a method of removing native oxide with an atomic layer of titanium underlying nickel and a capping titanium nitride layer in the process of forming a nickel silicide film.
In accordance with the objects of the invention a novel method for forming a high quality nickel silicide film in the fabrication of an integrated circuit is achieved. A semiconductor substrate is provided having silicon regions to be silicided wherein a native oxide layer forms on the silicon regions. A nickel layer is deposited overlying the silicon regions to be silicided. A titanium layer is deposited overlying the nickel layer. The substrate is annealed whereby titanium atoms from the titanium layer diffuse through the nickel layer and react with the native oxide layer and whereby the nickel is transformed to nickel silicide where it overlies the silicon regions and wherein the nickel not overlying the silicon regions is unreacted. In an alternative method, a titanium nitride layer over the titanium layer traps atmospheric oxygen freeing all of the titanium in the titanium layer to react with the underlying native oxide. The unreacted nickel layer is removed to complete formation of a nickel silicide film in the manufacture of an integrated circuit.
Also in accordance with the objects of the invention, another novel method for forming a high quality nickel silicide film in the fabrication of an integrated circuit is achieved. A semiconductor substrate is provided having silicon regions to be silicided wherein a native oxide layer forms on the silicon regions. A monolayer of titanium is deposited by atomic layer chemical vapor deposition overlying the silicon regions to be silicided. A nickel layer is deposited overlying the titanium monolayer. The substrate is annealed whereby titanium atoms from the titanium monolayer react with the native oxide layer and whereby the nickel is transformed to nickel silicide where it overlies the silicon regions and wherein the nickel not overlying the silicon regions is unreacted. In an alternative method, a titanium nitride layer over the nickel layer traps atmospheric oxygen. The unreacted nickel layer is removed to complete formation of a nickel silicide film in the manufacture of an integrated circuit.